Thin film membranes with additives for forward and pressure retarded osmosis

ABSTRACT

A thin film composite or TFC membrane formed by interfacial polymerization of an organic and aqueous phase on a support membrane with nanoparticles in the discrimination layer and/or the support membrane, optimized by the selection of nanoparticles for membrane flux, hydrophilicity and to minimize thickness of the support membrane while maintaining the strength and ruggedness characteristics required for forward osmosis (FO) and/or pressure retarded osmosis (PRO) so that the flux flow paths are less tortuous than conventional support membranes and thereby provide increased flux flow.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of provisional application61/050,572, filed May 5, 2008 and Ser. No.12/424,533 filed Apr. 15,2009, incorporated in herein in full and attached hereto as Appendix Afor that purpose.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is related to thin film composite membranes, which may becalled TFC membranes, and more particularly to such membranes used forforward osmosis or FO, for example to purify water, or for pressureretarded osmosis or PRO, for example to generate power from the mixingof salt water and pure water.

2. Description of the Prior Art

RO membranes are often made by interfacial polymerization or IFP of amonomer in a nonpolar (e.g. organic) phase together with a monomer in apolar (e.g. aqueous) phase on a porous support membrane. The supportmembrane is used for structural support of the IFP membrane duringmanufacturing and during operation. RO membranes, such as IFP ROmembranes (that is, RO membranes made by interfacial polymerizationprocesses), may be used for osmosis where water flows naturally from apure solvent or feed solution, to a less pure solution or draw solution.However, when IFP RO membranes are used for FO or PRO, the solvent,typically water, and the solute, typically water diluted with inorganicor organic salts, or other soluble molecules, tend to dilute each otherand reduce membrane efficiency. Further, the support membrane, which isused primarily for structural support, reduces water flux to somedegree, and the solvent and solute become mixed in solution in thethickness of the support membrane structure including a fabric, furtherreducing membrane efficiency for both FO and PRO processes.

What are needed are improved membranes with enhanced efficiency for usein FO and PRO processes.

SUMMARY OF THE INVENTION

In one aspect, a forward or pressure retarded osmosis process mayinclude providing a porous support membrane having nanoparticles and/orother additives disposed therein, applying a draw solution to one sideof a discrimination membrane interfacially polymerized on the poroussupport membrane and applying a feed solution to another side of thediscrimination layer for diffusion there through to remove contaminantsfrom, or utilize increased pressure in, the draw solution. The feedsolution may be applied to the porous support membrane for the anotherside of the discrimination layer.

The increased pressure in the draw solution resulting from transport ofthe feed solution across the discrimination membrane into the drawsolution may be used. Contaminants from the feed solution may be removedresulting from transport of the contaminants across the discriminationmembrane into the draw solution.

The porous support membrane may have the structural strength of athicker porous support membrane or a less porous support membrane as aresult of having the nanoparticles and/or other additives disposedtherein. A thinner support membrane, and/or a membrane with lesstortuous feed solution transport paths may be used as a result of havingthe nanoparticles and/or other additives disposed therein.

The discrimination membrane may including additives dispersed thereinadded to an organic and/or an aqueous phase before the organic andaqueous phases were contacted during the interfacial polymerization sothat the discrimination layer has increased feed solution permeabilityas a result of the additives therein. The discrimination membrane mayinclude the same or different nanoparticles and/or alkaline earth metalsand/or other metals and/or mhTMC as an additive dispersed therein. Themembrane may have increased feed solution permeability as a result ofthe additives therein. The draw solution may be seawater and the feedsolution may be fresh water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded diagrammatic view of membrane 10 during afabrication processing including nanoparticle/additives 16 in aqueousphase 14 and/or organic phase 18 and/or porous support 12 and/or fabric20.

FIG. 2 is a cross-sectional view of membrane 10 withnanoparticle/additives 16 dispersed in discrimination layer 24 andsupport layer 12.

FIG. 3 is a graph of resistance to flow, illustrating compaction as afunction of time, during initial operations of control membrane52—without nanoparticles/additives 16—and for membranes 54, 56 and 58with nanoparticle/additives 16 dispersed in various layers.

FIG. 4 is a photomicrograph illustrating the operation of the dual beamFIB-SEM technique used for FIGS. 5-7.

FIG. 5 is an FIB-SEM of support membrane 12—with nanoparticle/additives16 dispersed therein—after 8 hours of operation of membrane 12 at 800psi.

FIGS. 6,7 are FIB-SEMs of support membrane 64, withoutnanoparticle/additives 16 dispersed therein, after 1 and 8 hours ofoperation, respectively.

FIG. 8 is a diagrammatic view of an IFP FO/PRO membrane in aconventional cylindrical housing, canister 66.

FIG. 9 is a diagrammatic view of membrane 10 during operation as an FOor RO membrane including a graph of salinity superimposed thereon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to FIG. 1, an exploded view of membrane 10 illustratingthe fabrication process is shown in which membrane 10 may includeorganic phase layer 18, aqueous phase layer 14, porous support membrane12 and fabric layer 20. One or more types of nanoparticles 16, or otheradditives as discussed below in greater detail, may be included inaqueous or organic phases 14, 18 before contact there between forinterfacial polymerization so that nanoparticles 16 are dispersed indiscrimination layer 24 as shown in FIG. 2. Nanoparticles/additives 16may also be dispersed in support layer 12 and fabric 20.

Referring now also to FIG. 2, a portion of membrane 10 is illustratedafter fabrication including nanoparticles and/or other additives 16, indiscrimination layer 24 as well as nanoparticles/additives 16 in supportlayer 12 which may be the same or different than those—if any—used indiscrimination layer 24. In a conventional thin film composite or TFCmembrane, made without nanoparticles/additives 16, the typical layerthicknesses are as shown, the discrimination layer is on the order of0.1 microns (100 nm) thick, the support layer is typically on the orderof 50 microns thick and the fabric layer is typically on the order of100 microns thick. These thicknesses of layers are conventionallyrequired for structural support.

Nanoparticles/additives 16, which may used in porous support layer 12 toadd strength to support membrane 12, advantageously may permit asubstantially thinner support membrane to be used under the sameconditions as a conventionally made support membrane is used asdiscussed in more detail below. Similarly, the same or differentnanoparticles 16 may be added to fabric layer 20 to provide furtherstructure support and ease of handling for support membrane 12 andmembrane 10. For example, the conventionally used 50 micron thickness ofsupport layer for TFC membranes, such as membrane 10, when strengthenedby the addition of nanoparticles 16, provides perhaps twice as muchstructural strength as provided by the same support layer withoutnanoparticles/additives 16 and may be replaced by a substantiallythinner layer such as a 25 micron layer without any loss of requiredstrength as shown below with regard to FIG. 9. Similarly, whennanoparticles/additives 16 are added, the thickness of fabric 20 may bereduced by perhaps about 25% to 50% as also shown below in FIG. 9.

During fabrication, support membrane 12 is often formed by casting onfabric 20. Nanoparticles/additives 16 may be added to aqueous phase 14and/or organic phase 18 before such phases are contacted together forIFP. Aqueous phase 14 is typically applied to support 12 and thenorganic phase 18 is applied to aqueous phase 14 which begins the IFPprocess, forming discrimination layer 24.

In particular with regard to the process of forming membrane 10 by IFP,aqueous phase 14 may also include one of the reactants or monomers, andother processing aids such as surfactants, drying agents, catalysts,coreactants, cosolvents, etc. A first reactant or monomer can beselected so as to be miscible with a polar liquid to form a polarmixture. Typically, the first monomer can be a dinucleophilic or apolynucleophilic monomer. Generally, the difunctional or polyfunctionalnucleophilic monomer can have a primary or secondary amino group and canbe aromatic (eg, m-phenylenediamine (MPD), pphenylenediamine,1,3,5-triaminobenzene, 1,3,4-triaminobenzene, 3,5-diaminobenzoic acid,2,4-diaminotoluene, 2,4-diaminoanisole, and xylylenediamine) oraliphatic (e.g., ethylenediamine, propylenediamine, piperazine, andtris(2-diaminoethyl)amine).

The polar mixture for aqueous phase 14 need not be aqueous, but thepolar liquid should be immiscible with the apolar liquid of organicphase 18. Although water is a preferred solvent for aqueous phase 14,non-aqueous solvents can be utilized, such as acetonitrile anddimethylformamide (DMF). The resulting polar mixture typically includesfrom about 0.1% to about 20% by weight, preferably from about 0.5% toabout 6% weight, of amine. The polar mixture can typically be applied tothe micro-porous support membrane 12 by dipping, immersing, coating,spraying or other conventional techniques. Once coated on porous supportmembrane 12, excess polar mixture can be optionally removed byevaporation, drainage, air knife, rubber wiper blade, nip roller,sponge, or other devices or processes.

Organic phase 18 used during IFP may also include one of the reactantsand other processing aids such as catalysts, co-reactants, co-solvents,etc. A second monomer can be selected so as to be miscible with anapolar liquid forming an apolar mixture for organic phase 18, althoughfor monomers having sufficient vapor pressure, the monomer can beoptionally delivered from a vapor phase. Typically, the second monomercan be a dielectrophilic or a polyelectrophilic monomer. Theelectrophilic monomer can be aromatic in nature and can contain two ormore, for example three, electrophilic groups per molecule. For the caseof acyl halide electrophilic monomers, acyl chlorides are generally moresuitable than the corresponding bromides or iodides because of therelatively lower cost and greater availability.

Suitable polyfunctional acyl halides include trimesoyl chloride or TMC,trimellitic acid chloride, isophthaloyl chloride, terephthaloyl chlorideand similar compounds or blends of suitable acyl halides. Thepolyfunctional acyl halide can be dissolved in an apolar organic liquidfor organic phase 18 in a range of, for example, from about 0.01% toabout 10.0% by weight or from about 0.05% to about 3% weight percent,preferably about 08.%-5.0%. Suitable apolar liquids are those which arecapable of dissolving the electrophilic monomers, for examplepolyfunctional acyl halides, and which are immiscible with a polarliquid, for example water. In particular, suitable apolar liquids caninclude those which do not pose a threat to the ozone layer and yet aresufficiently safe in terms of their flashpoints and flammability toundergo routine processing without having to undertake extremeprecautions. Higher boiling hydrocarbons, e.g., those with boilingpoints greater than about 90° C., such as C8-C24 hydrocarbons andmixtures thereof, have more suitable flashpoints than their C5-C7counterparts, but they are less volatile. The apolar mixture for organicphase 18 can typically be applied to microporous support membrane 12 bydipping, immersing, coating or other conventional techniques.

During fabrication of membrane 10, interfacial polymerization—orIFP—occurs at the interface between aqueous phase layer 14 and organicphase layer 18 to form discrimination layer 24 shown in FIG. 2. Theconventional conditions for the reaction of MPD and TMC to form a fullyaromatic, polyamide thin film composite membrane 10 include an MPD toTMC concentration ratio of 10-30 with MPD at about 1% to 6% by weight inpolar phase 14, preferably about 2.0-4.0% by weight MPD. The reactioncan be carried out at room temperature in an open environment, or thetemperature of either the polar or the apolar liquid or both may becontrolled.

Once formed, the dense polymer layer, which becomes discrimination layer24, can advantageously act as a barrier to inhibit the contact betweenreactants and to slow down the reaction. The selective dense layer,discrimination layer 24 so formed, is typically very thin and permeableto water, but relatively impermeable to dissolved, dispersed, orsuspended solids such as salts. Once the polymer layer 24 is formed, theapolar liquid or residue of organic phase 18 can be removed byevaporation or mechanical removal. It is often convenient to remove theresidue of organic phase 18 by evaporation at elevated temperatures, forinstance in a drying oven.

Nanoparticles/additives 16 may be added to aqueous phase 14 and/ororganic phase 18 for several reasons; to increase water permeability, toincrease hydrophilicity, and/or to control surface morphology (forexample to increase or decrease the smoothness of the membrane surface).Changes to the membrane smoothness can alter the rate at which materialsrejected by the membrane are transported from the membrane, that is,higher smoothness can both improve process efficiency and/or reducefouling.

In some cases, performance can be further improved by the addition of arinse in a high pH aqueous solution after membrane 10 is formed. Forexample, membrane 10 can be rinsed in a sodium carbonate solution. ThepH is preferably from 8-12, and exposure time may vary from 10 secondsto 30 minutes or more. Alternatively the membrane may be rinsed at hightemperatures, or exposed to chlorinating agents.

Support membrane 12, on which discrimination layer 24 is formed by IFP,is typically a polymeric microporous support membrane, which may or maynot be supported by a nonwoven or woven fabric, such as fabric 20, forfurther mechanical strength and structural support. Support membrane 12may conventionally be made from polysulfone or other suitably porousmembranes, such as polyethersulfone, poly(ether sulfone ketone),poly(ether ethyl ketone), poly(phthalazinone ether sulfone ketone),polyacrylonitrile, polypropylene, cellulose acetate, cellulosediacetate, or cellulose triacetate. These conventional microporoussupport membranes 12 are typically 25-250 microns in thickness, forexample 50 microns, and have been found to have the smallest poreslocated very near their upper surface. Porosity at the surface ofmembrane 12 is often low, for instance from 5-15% of the total surfacearea. Nanoparticles/additives 16, such as zeolites, particularly LTA,may be added to support membrane 12 during processing to improve fluxby, perhaps, improving porosity, e.g. at the surface of support membrane12 and/or by making membrane 12 more resistant to compaction and/ormechanical strengthening of the membrane.

Support membrane 12 including nanoparticles/additives 16 will havegreater strength and toughness and therefore may be made thinner thanconventional support membranes made for the same service. As a result ofbeing thinner, support membranes 12 with nanoparticles/additives 16imbedded therein are able to minimize mixing within the support andfabric layer, possibly from the decreased diffusion path length.Further, addition of nanoparticles 16 to the support membrane 12 maylead to a more highly porous structure, with fluid transport paths ofrelatively low tortuosity, when compared with a conventional supportmembrane.

In other words, support membrane 12 with nanoparticles/additives 16 maybe made thinner using less material (and thus possessing more porosity,less thickness and less tortuosity of water flow path) while stillproviding the required mechanical properties to serve as an appropriatesupport. In one embodiment, this may be accomplished, for example, byforming porous support membrane 12 from a polymer andnanoparticle/additive solution containing less polymer, for example5-15%, than would be used in conventional support membranes 12, such as15-20%. In another embodiment, this may be accomplished, for example, bycasting a thinner layer directly, for instance by changing the gap usedfor slot die or knife over roll casting, or by decreasing the flow rateor increasing the web speed for slot die casting.

Support layers 12—including well dispersed nanoparticles/additives 16therein—may also be hydrophilic, e.g., with surfaces more readily wetwith water and/or displacing air or gasses entrained within the body ofsupport 12. Such entrained gasses may make support 12 less efficient byblocking portions of support 12 to water flow, reducing effectiveporosity of support 12 to water or other fluid flow. By selectingnanoparticles/additives 16 for use within support membrane 12 thatresult in hydrophilicity of membrane 12 (for example nanoparticlezeolites such LTA), increased hydrophilicity of support 12 may result inreduced water contact angles at the surfaces of support 12.

In some instances, fabric layer 20 may also have nanoparticles/additives16 incorporated therein for added strength, as shown for example belowwith regard to FIG. 9. Fabric layer 20 may be woven or non-woven layerstypically of polymeric fibers. It is desirable that fabric layer 20 bepermeable to the fluid or water being processed, flat and without strayfibers that could penetrate support 12 and/or thin film 24 and relativethin to decrease cost and to maximize the surface area of membrane 10for a given diameter housing as discussed below in greater detail withregard to FIG. 8, strong against extension and mechanically resistant todeformation at high pressures which is useful for PRO processes in whichthe draw solution is often pressurized to enable more efficient systemperformance. Adding nanoparticles/additives 16 to the polymer fibers oflayer 20 produces a more mechanically robust backing that may allowthinner, less expensive, or tougher support layers to be manufactured aswell as help increase the surface area of membrane 10 for a givendiameter housing as described with regard to FIG. 8. In some cases itmay be preferable that fabric layer 20 is contained within the supportlayer 12.

In some instances, membrane 10 may be used to treat waters that containmaterials that have a tendency to accumulate on the membrane surface,decreasing the effective permeability of the membrane. These materialscan include but are not limited to natural organic matter, partiallyinsoluble inorganic materials, organic surfactants, silt, colloidalmaterial, microbial species including biofilms, and organic materialseither excreted or released from microbial species such as proteins,polysaccharides, nucleic acids, metabolites, and the like. This drop inpermeability is often smaller for membranes prepared as disclosed hereinthan for membranes prepared by conventional techniques due to adecreased amount, density, viability, thickness and/or nature ofaccumulated material. Membrane surface properties, such ashydrophilicity, charge, and roughness, often affect this accumulationand permeability change.

Generally, membranes with highly hydrophilic, negatively charged andsmooth surfaces yield good permeability, rejection, and foulingbehavior. The improved resistance to accumulation for membranes of thetype disclosed herein can in part be related to the increasedhydrophilicity of these membranes. The increased hydrophilicity can bemeasured by the equilibrium contact angle of the membrane surface with adrop of distilled water at a controlled temperature. Membranes preparedwith nanoparticles/additives 16 present during IFP polymerization canhave a contact angle that is reduced by 5°, 15° or even 25° or morerelative to a similarly prepared membrane withoutnanoparticles/additives 16. The equilibrium contact angle can be lessthan 45°, less than 40°, or even less than 25°.

Contact angles of distilled, or DI, water at room temperature may bemeasured. Membrane 10 may be thoroughly rinsed with water, and thenallowed to dry in a vacuum desiccator to dryness. Membrane 10 may bedried in a vertical position to prevent re-deposition of any extractedcompounds that may impact contact angle. Due to the occasionalvariability in contact angle measurements, 12 angles may be measured atdifferent spots on membrane 10 with the high and low angles beingexcluded and the remaining angles averaged.

Referring now to FIGS. 3-6, the addition of nanoparticles/additives 16to support layer 12, and/or fabric layer 20, may reduce the tendency ofmembrane 10 to become compacted overtime and lose permeability duringoperation.

Compaction is a somewhat different function or result than the increasedstrength of support membrane 12 discussed above. The increased strengthof support 12 discussed above resulting from the addition ofnanoparticles/additives 16 refers to the fact that membrane 12 withnanoparticles/additives 16 dispersed therein provides greater supportand resistance against damage and distortion. As a result, for example,a typical 50 micron thickness of support membrane 12, fabricated withoutnanoparticles/additives 16 may be replaced with a 25 micron thickness ofthe same membrane with nanoparticles/additives 16 dispersed thereinwithout loss of the necessary structural strength or rigidity.

As described immediately below, resistance to compaction refers to theability of membrane 12, with nanoparticles/additives 16 dispersedtherein, to resist being compacted, i.e., being squeezed to a thinnerdimension by pressure and remaining at a thinner dimension. As shownbelow with regard to the graph of FIG. 3, membrane 12 withnanoparticles/additives 16 is substantially less compacted over timeduring operation as a result of applied pressure. The advantage ofresistance to compaction is a reduction in the common loss, afterinitial operation, of substantial permeability or flux flow. Theadvantage of increased strength by adding nanoparticles/additives 16 tosupport membrane 12, and/or fabric 20, is that a thinner supportmembrane, with shorter and less tortuous flow paths, may be used andprovides better operating efficiency for FO and PRO processes bothduring initial operation and also thereafter.

Referring now in particular to FIG. 3, graph 50 illustrates flowcompaction by graphing resistance to flow through membrane 12 withnanoparticles/additives 16, as a function of time. The experimentalconditions were a differential pressure of 500 pounds per square inch orpsi, a temperature of 25° C. and 585 ppm NaCl. For control membrane 52,a TFC membrane similar to membrane 10 except withoutnanoparticles/additives 16 dispersed therein was used, as shown by thegraph line for membrane 52. Resistance increased from just above 6 unitsto about 12.5 or so units in about 2 hours. That is, after initialoperation, the TFC membrane made in accordance with the presentdisclosure but without nanoparticles/additives 16 lost about half of itspermeability in about 2 hours. Membrane salt rejection was on the orderof 91%.

The graph line for membrane 54, with nanoparticles/additives 16dispersed in discrimination layer 24, indicates that the resistance toflow in membrane 54 started at a much lower resistance to flow, justover 4 units, and lost very little permeability over the 4 hour test.Membrane salt rejection was on the order of 90%.

The graph line for membrane 56, with nanoparticles/additives 16 insupport layer 12 and discrimination layer 24, indicates that theresistance to flow in membrane 56 started at an even lower resistance toflow, about 1.5 units, and also lost very little permeability over the 4hour test. Membrane salt rejection was on the order of 94%.

The graph line for membrane 58, with nanoparticles/additives 16 insupport layer 12, indicates that the resistance to flow in membrane 58started at an even lower resistance to flow, just about 1 unit, and losta little permeability over the 4 hour test, to reach the same level asmembrane 56 in about 1 hour. Membrane salt rejection was on the order of92%.

Graph lines for the 4 membranes shown in graph 50 illustrate the reducedresistance to flow for a TFC membrane, such as membrane 52, whennanoparticles/additives 16 are added to the various layers in membranes54, 56 and 58, indicating that the addition of nanoparticles/additives16 increases the resistance to compaction of these membranes.

Referring now in particular to FIGS. 4-7, a series of photomicrographsare shown of various support membranes taken by a focused ion beamscanning electron microscope or FIB-SEM technique, to illustrate thephysical effect of the presence of nanoparticles/additives 16 in supportmembrane 12 over time. In this technique, as shown in FIG. 4, platinumdeposition Pt 60 was made on a sample polysulfone support membrane 64and a dual ion beam was used to cut a cross sectional view of thepolysulfone support to a depth of approximately 5 microns. A portion ofcut 62 for 3 different membranes is shown by FIB-SEM in FIGS. 5-7.

Referring now specifically to FIGS. 5-7, a segment of support membrane12—with nanoparticles/additives 16 dispersed therein—is shown by FIB-SEMafter 16 hours of operation at 800 psi. For comparison, control membrane64, made in the same manner as membrane 12 but withoutnanoparticles/additives 16, is also shown after 1 hour of operation at800 psi. The openings in membranes 12 and 64 are generally of the sameshape and orientations. FIG. 7 shows membrane 64 after 8 hours ofoperation at the same pressure, 800 psi. The shape and orientation ofthe openings within membrane 64 have clearly been degraded during thesubsequent operations. In particular, the openings shown in FIG. 7 areprimarily in a horizontal orientation indicating that substantialcompaction has occurred compared to the openings in membrane 64 shown inFIG. 6.

It is clear by comparing support membrane 12 in FIG. 5 that very littlecompaction has occurred in the membrane with nanoparticles/additives 16after 16 hours because at least a fair number of the openings areclearly oriented in a vertical direction as also shown in membrane 64 inFIG. 6 rather than primarily in a horizontal orientation as shown bymembrane 64 in FIG. 7 after 8 hours.

In operation, saltwater 26 could also be a relatively high concentrationstream of any solute rejected by membrane 10, such as less pure water,and able to generate a spontaneous flow into pure fluid 28. Similarly,pure fluid 28 could be any stream relatively low in concentration ofsolutes rejected by membrane 10, for example a freshwater solution. Insome instances, pure water 28 could even be seawater if a sufficientconcentration of solutes are added to saltwater 26 to cause water toflow from fluid 28 to 26. Alternately, saltwater 26 could be relativelypure water with a high quantity of sugars present to desalinate aseawater stream into a potable mixture, or a high quantity of ammoniumcarbonate which can easily be removed by subsequent processing togenerate a purified water stream. In a PRO system, the pressure could beutilized at tap 68.

Support membranes 12 with nanoparticles/additives 16 imbedded thereinmay be able to minimize mixing losses from purified water 28 andseawater 26 by maximizing diffusive transport of solutes within support12. Inclusion of nanoparticles/additives 16 in support 12 may addstrength and toughness allowing useful support membranes 12 to becreated from materials that would conventionally be ineffective such aspolypropylene, polyethyleneterepthalate, polyvinylchloride, orpolystyrene.

Referring now to FIG. 8, canister 66 may be a conventional membranecanister such as a 8″ diameter, 40″ long sealed tube containing solute,such as seawater 26, surrounding membrane structure 72 wound in a spiralaround flow tube 70 carrying the solvent, such as purified water 28.Membrane structure 72 may include one or more sheets of 12″-40″ widesheets of membrane 10 that are 20″-80″ long, providing a wide range oftotal surface areas from about 5 square feet to 1600 square feet ormore, plus conventional spacers, permitting membrane 10 to be wound in aspiral form. Membrane 10 may include support layer 12 withnanoparticles/additives 16 dispersed therein having a reduced thickness,for example, of 25 microns rather than the conventional 50 microns asshown in FIG. 2 as well as fabric 20 with nanoparticles/additives 16dispersed therein having a reduced thickness of for example 75 micronsrather than the conventional 100 microns also as shown in FIG. 2.

Because of the spiral winding, the benefit of the additional strengthprovided by nanoparticles/additives 16 reduces the diameter of thespiral wound membrane structure 72 by 50 microns for each winding. Aconventional membrane of the same type as membrane 10 having a 50 micronsupport membrane and a 100 micron fabric backing that would fit inconventional canister 66 would have the same 40″ width as membrane 10but the total square footage of membrane available for osmosis would bereduced by ˜3-10% compared to a membrane fabricated according to thepresent disclosure. In other words, the use of nanoparticles/additives16 in support membrane 12 and/or fabric 20 may provide a ˜3-10%improvement in the membrane area available for osmosis when used in astandard size canister.

Referring now to FIG. 9, FO/PRO membrane 10 is shown in operationbetween draw solution 26 and feed solution 28 to illustrate a furtheradvantage, related to salinity, of the addition nanoparticles/additives16 to permit the use of thinner support layers 12 and/or thinner fabriclayers 20. Membrane 10 may be used for FO or PRO processes in which feedsolution 28 may be allowed to spontaneously flow through membrane 10 todilute draw solution 26 on the other side of membrane 10. To a smalldegree, salt or other contaminants from draw solution 26 can alsodiffuse into feed solution 28 and vice versa. These processes lead toregions within draw solution 26 diluted with feed solution 28 andregions in support membrane 12, fabric 20 and feed solution 28contaminated with draw solution 26. FIG. 9 includes a graph of salinity25 superimposed on the illustration of FO/PRO membrane 10 in use.

In the graph, salinity 25 increases from the left hand side to amaximum, such as 32,000 ppm of salt in saltwater 25. The increasingsalinity shown is the salinity of the fluid at the vertical positionwithin saltwater 26, membrane 10 including support 12 and fabric 10, andfresh water 28. Graph segment 25 a represents a portion of the salinitycurve where saltwater 26 contacts discrimination membrane 24. As shownby segment 25 a, salinity decreases from the maximum salinity of thesaltwater to a lower salinity where pure water 28, having penetrateddiscrimination membrane 24, is not yet fully in solution with saltwater26. Below discrimination membrane 24, graph segment 25 b illustratessalinity 25 substantially reduced by membrane 10 but still higher thanthe salinity of pure water 28. The salinity gradually reduces as thesalt from saltwater 26, leaking backwards through membrane 10, isdissolved in pure water 28 until it reaches the typically non-zero levelof salt in pure water 28. The salinity for segment 25 b is also higherthan that in pure water 28 from removal of water through thediscrimination membrane 24.

Although membrane 10 is shown with discrimination membrane 24 in contactwith seawater 26, fabric 20 in contact with fresh water 28, and withsupport membrane 12 there between, it is conventional in some situationsto use membrane 10 in the opposite orientation. That is, discriminationmembrane 24 may be in contact with fresh water 28, fabric 20 in contactwith seawater 26, and support membrane 12 there between.

Referring again to the orientation shown in FIG. 9, the presence of purewater 28 in saltwater 26 above membrane 10, and of salt from saltwater26 in pure water 28 near the bottom of discrimination layer 24, reducesthe efficiency of FO and PRO processes across membrane 10 by reducingthe salinity differential there across. It should be noted that amongthe advantages of membrane 10 as described herein, the presence ofnanoparticles/additives 16 in support layer 12 (and/or fabric 20)enhance the strength of these structural layers permitting the use ofthinner layers. Further, in addition to support layer 12 being thinner,the water transport paths there through may become less tortuous, i.e.,less resistant to flow, and therefore make support layer 12 morepermeable than a conventional porous support membrane.

Although the exact thickness dimensions of the various layers ofconventional FO and PRO membranes depend on many factors, the followingtable shows some relatively reasonable, representative values of thethicknesses and salinity of conventional IFP RO membranes and IFP ROmembranes 10—with nanoparticles/additives 16 dispersed therein—inaccordance with the present disclosure as a guide to one of theimprovement provided by the present design. A salinity of 32,000 partsper million, or ppm, for saltwater 26 and 500 ppm for fresh water 28 wasused.

Salinity ppm at IFP FO/PRO Support Fabric Membrane 10 Salinity Membranes(in Microns) Top Bottom Differential Conventional 50 75 25K   5K   20KNanoparticle 25 50 25K 1.5K 23.5K

Although the mixing of fresh water and salt water in FO and PROprocesses conventionally leads to decreased driving forces for watertransport, leading to decreased process efficiencies, the use ofnanoparticles in discrimination layer 24, support layer 12 and/or inother layers such as fabric layer 20, as described herein, may increasethe concentration driving force and improve process efficiencies. Forexample, use of nanoparticles and/or other additives dispersed indiscrimination layer 24 and/or support layer 12 may lead to increasedflux flow or permeability to further increase process efficiencies.

Referring now to Appendix A, and in particular to Section D: TablesI-XII, Examples 1-172, pages 66-77, par.s [00047]-[000259], the relatedportions of the specification and drawings of Appendix A, and FIGS. 1and 2 of the present application, nanoparticles/additives 16,particularly for addition to aqueous phase 14 and/or organic phase 18before IFP in order to be dispersed in discrimination layer 24, mayinclude

-   -   LTA nanoparticles 16 in aqueous phase 14 as indicated in        examples 23-25 and/or in organic phase 18 as shown in examples        26-28;    -   CuMOF nanoparticles in organic phase 18 as indicated in example        36;    -   SiO2 nanoparticles 16 in aqueous phase 14 as indicated in        example 38;    -   Zeolite BETA nanoparticles 16 in aqueous phase 14 as indicated        in example 40;    -   additives such as Al, Fe, Sn, Cu, Co, Pr, Zn, Cr, In, V, Sn, Ru,        Mo, Cd, Pd, Hf, Nd, Na, Yb, Er, Zn, K and/or Li in organic phase        18 as indicated in examples 94-118;    -   mhTMC in organic phase 18 as indicated in examples 122-136;    -   Alkaline earth additives in organic phase 18, such as Ca, Sr, Mg        or Be as indicated in examples 29-34;    -   Nanotubes in organic phase 18 as indicated in example 44;    -   mhTMC (monohydrolyzed TMC) in organic phase 18 as shown in        examples 122-136; as well as    -   combinations of these nanoparticle/additives, such as        nanoparticles (including FAU) or nanotubes with metal additives        or alkaline earth additive and/or with mhTMC as indicated in the        remaining examples in Tables I-X.

Further, the concentration of TMC may be adjusted in accordance with theranges indicated in examples 137-166 in Table XI, as described ingreater detail in Appendix A, and the MPD to TMC ratio may be adjustedin accordance with the ratios shown in Table XII, as described ingreater detail in Appendix A.

Further, the combination of nanoparticle and other additive reduces fluxloss during initial operation as shown in FIG. 5, as described ingreater detail in Appendix A.

Still further, the concentration of additives and combinations thereof,such as mhTMC, can be adjusted, tested and compared to identify thedeflection point as shown in FIG. 26, as described in greater detail inAppendix A. Knowledge of the deflection point, where one can be clearlydetermined, for a particular additive or combination of additives,permits optimizing the select of the additives, whether nanoparticles ortubes, alkaline earth or other metals, mhTMC and/or various combinationsthereof.

1. A forward or pressure retarded osmosis process, comprising: providinga porous support membrane having nanoparticles disposed therein;applying a draw solution to a discrimination membrane interfaciallypolymerized on the porous support membrane; and applying a feed solutionto the discrimination layer for diffusion there through to the drawsolution to remove contaminants from, or utilize increased pressure in,the draw solution.
 2. The forward or pressure retarded osmosis processof claim 1, wherein applying a draw solution to a discriminationmembrane interfacially polymerized on the porous support membranefurther comprises: applying the draw solution to the porous supportmembrane for diffusion there through to the discrimination layer.
 3. Theforward or pressure retarded osmosis process of claim 1, whereinapplying a feed solution to the discrimination layer for diffusion therethrough into the draw solution, comprising: applying the feed solutionto the porous support membrane for diffusion there through to thediscrimination layer.
 4. The forward or pressure retarded osmosisprocess of claim 1, further comprising: utilizing increased pressure inthe draw solution resulting from transport of the feed solution acrossthe discrimination membrane into the draw solution.
 5. The forward orpressure retarded osmosis process of claim 1, further comprising:contaminants may be removed from the feed solution resulting fromtransport of the contaminants across the discrimination membrane intothe draw solution.
 6. The process of claim 1, wherein providing a poroussupport membrane having nanoparticles disposed therein furthercomprises: providing a porous support membrane having the structuralstrength of a thicker porous support membrane as a result of having thenanoparticles disposed therein.
 7. The process of claim 1, whereinproviding a porous support membrane having nanoparticles disposedtherein further comprises: providing a porous support membrane havingthe structural strength of a more porous support membrane as a result ofhaving the nanoparticles disposed therein.
 8. The process of claim 1,wherein providing a porous support membrane having nanoparticlesdisposed therein further comprises: providing a thinner porous supportmembrane having the required structural strength for the process as aresult of having the nanoparticles disposed therein.
 9. The process ofclaim 1, wherein providing a porous support membrane havingnanoparticles disposed therein further comprises: providing a poroussupport membrane having less tortuous feed solution transport paths as aresult of having the nanoparticles disposed therein.
 10. The process ofclaim 1, wherein providing a porous support membrane havingnanoparticles disposed therein further comprises: providing a poroussupport membrane having increased hydrophilicity as a result of havingthe nanoparticles disposed therein.
 11. The process of claim 1, furthercomprising: providing the discrimination membrane including additivesdispersed therein added to an organic and/or an aqueous phase before theorganic and aqueous phases were contacted during the interfacialpolymerization so that the discrimination layer has increased solventpermeability as a result of the additives therein.
 12. The process ofclaim 11 wherein providing the discrimination membrane includingadditives dispersed therein further comprises: providing thediscrimination membrane including the same or different nanoparticlesdispersed therein.
 13. The process of claim 12 wherein providing thediscrimination membrane including the same or different nanoparticlesdispersed therein further comprises: providing the discriminationmembrane also including alkaline earth metals dispersed therein.
 14. Theprocess of claim 12 wherein providing the discrimination membraneincluding the same or different nanoparticles dispersed therein furthercomprises: providing the discrimination membrane also including alkalineearth metals dispersed therein.
 15. The process of claim 13 whereinproviding the discrimination membrane also including alkaline earthmetals dispersed therein further comprises: providing the discriminationmembrane also including mhTMC as an additive dispersed therein.
 16. Theprocess of claim 11 wherein providing the discrimination membraneincluding additives dispersed therein further comprises: providing thediscrimination membrane including alkaline earth metals dispersedtherein.
 17. The process of claim 16 wherein providing thediscrimination membrane including alkaline earth metals dispersedtherein further comprises: providing the discrimination membrane alsoincluding mhTMC as an additive dispersed therein.
 18. The process ofclaim 11 herein providing the discrimination membrane includingadditives dispersed therein further comprises: providing thediscrimination membrane including mhTMC as an additive dispersedtherein.
 19. The process of the claim 1, further comprising: providingthe discrimination membrane including additives dispersed therein addedto an organic and/or an aqueous phase before the organic and aqueousphases were contacted during the interfacial polymerization so that thediscrimination layer has increased solvent permeability as a result ofthe additives therein.
 20. The process of claim 1, wherein the drawsolution is seawater and the feed solution is fresh water.